using CommandLine;

using MultiversalDiplomacy.Script;

namespace MultiversalDiplomacy.CommandLine;

[Verb("repl", HelpText = "Begin an interactive 5dplomacy session.")]
public class ReplOptions
{
    [Option('i', "input", HelpText = "Begin the repl session by executing the commands in this file.")]
    public string? InputFile { get; set; }

    [Option('o', "output", HelpText = "Echo the repl session to this file. Specify a directory to autogenerate a filename.")]
    public string? OutputFile { get; set; }

    public static void Execute(ReplOptions args)
    {
        IEnumerable<string>? inputFileLines = null;
        if (args.InputFile is not null) {
            var fullPath = Path.GetFullPath(args.InputFile);
            inputFileLines = File.ReadAllLines(fullPath);
            Console.WriteLine($"Reading from {fullPath}");
        }

        // Create a writer to the output file, if specified.
        StreamWriter? outputWriter = null;
        if (args.OutputFile is not null)
        {
            string fullPath = Path.GetFullPath(args.OutputFile);
            string outputPath = Directory.Exists(fullPath)
                ? Path.Combine(fullPath, $"{DateTime.UtcNow:yyyyMMddHHmmss}.log")
                : fullPath;
            Console.WriteLine($"Echoing to {outputPath}");
            outputWriter = File.CreateText(outputPath);
        }

        IEnumerable<string?> GetInputs()
        {
            foreach (string line in inputFileLines ?? [])
            {
                var trimmed = line.Trim();
                // File inputs weren't echoed to the terminal so they need to be echoed here
                Console.WriteLine($"{trimmed}");
                yield return trimmed;
            }

            string? input;
            do
            {
                input = Console.ReadLine();
                yield return input;
            }
            while (input is not null);
            // The last null is returned because an EOF means we should quit the repl.
        }

        IScriptHandler? handler = new ReplScriptHandler(Console.WriteLine);

        Console.Write(handler.Prompt);
        foreach (string? nextInput in GetInputs())
        {
            // Handle quitting directly.
            if (nextInput is null || nextInput == "quit" || nextInput == "exit")
            {
                break;
            }
            string input = nextInput.Trim();
            outputWriter?.WriteLine(input);
            outputWriter?.Flush();

            // Delegate all other command parsing to the handler.
            var result = handler.HandleInput(input);

            // Report errors if they occured.
            if (!result.Success)
            {
                Console.WriteLine($"Error: {result.Message}");
            }

            // Quit if the handler didn't continue processing.
            if (result.NextHandler is null)
            {
                break;
            }

            // Otherwise prompt for the next command.
            Console.Write(handler.Prompt);
        }

        Console.WriteLine("exiting");
    }
}